Dropping fuel pressure - will not stay where I set it

[linksys42]

Hello, I have been having this problem for a while now and I cannot figure it out. First off I will list my fuel mods. I have an 190l walbro FP rewired, and a Aeromotive AFPR this one http://www.importevolution.com/product_info.php?cPath=24_45&products_id=1620
The problem is that when I start the car the fuel pressure is set at 44 psi with the vac line off. After I drive for a bit and stop and check the fuel pressure again it drops off to 40-41psi? I have stopped driving the car because I am afraid im going to starve the engine for fuel. I cannot seem to find out why it is loosing pressure after the engine is warmed up and has been driving for a bit? I have pulled the pump and checked the o-ring and to make sure it would not slip or leak I installed multiple o-rings behind the spacer so that the spacer keeps pressure on the sealing o-ring at all times and reinstalled. Also replaced the crush washers on the fuel filter. And I do not have any leaks any where in the whole system. I have checked all the lines many of times. I am totally lost and cant find out what would be causing this? I would really appreciate any help you guy might have. I am at my wits end and am about to give up. Thanks again

 

[fourreGsixty3]

A likely place for it to be leaking from the adjusting rod, and vacuum fitting.

Set base fuel pressure, to 43.5psi. But before you set the base pressure, unscrew the vacuum fitting on the FPR and apply tafflon to the threads and reinstall. After you set the base pressure to around 43.5 ( or as close as you can), mark the adjustment rod where it meets the body of the fpr, remove the ajustment rod and wrap a liberal amount of tafflon around and right below the mark, reset your base pressure to 43.5 and make sure the tafflon tape covers the threads between the rod and FPR. Now tighten down the lock nut (be careful not to allow the adjustment rod to move with the lock nut), and leave the fpr alone.

This should prevent any leaking from your AFPR...thats where I believe it to be leaking from.

 

[oldman]

A likely place for it to be leaking from the adjusting rod, and vacuum fitting.

Set base fuel pressure, to 43.5psi. But before you set the base pressure, unscrew the vacuum fitting on the FPR and apply tafflon to the threads and reinstall. After you set the base pressure to around 43.5 ( or as close as you can), mark the adjustment rod where it meets the body of the fpr, remove the ajustment rod and wrap a liberal amount of tafflon around and right below the mark, reset your base pressure to 43.5 and make sure the tafflon tape covers the threads between the rod and FPR. Now tighten down the lock nut (be careful not to allow the adjustment rod to move with the lock nut), and leave the fpr alone.

This should prevent any leaking from your AFPR...thats where I believe it to be leaking from.

Cut and paste? This is what is missing from all the installation instructions. With that said, leaking vacuum fitting and adjustment rod should not change the base setting.

OP, are you using a liquid filled gauge?

 

[linksys42]

Cut and paste? This is what is missing from all the installation instructions. With that said, leaking vacuum fitting and adjustment rod should not change the base setting.

OP, are you using a liquid filled gauge?

Thanks for the reply’s guys! I’m about ready to pull my hair out because I can’t figure this out. Originally when I installed the AFPR I did Teflon all the fittings, adjustment screw and the vacuum nipple. I had read and researched a bunch of threads concerning the install and the problems with AFPR’s, like oldman’s post concerning the Teflon on the fittings. I am using a marshal liquid filled gage to set the base pressure. Its just really strange how the pressure just keeps dropping and having to bump it up then letting it sit and cool down for awhile then starting it back up and the base pressure jumping up from base pressure past 44 from me bumping the pressure when it fell to 40-41. I have never heard or read a thread of someone having a problem like this. I am leaning towards it having to do something with the heat. Thanks for the help.

 

[oldman]

Liquid filled gauges will drop about 2 psi when the liquid get hot and pressure builds inside the gauge. Set it cold and leave it, it will go back up to 43.5 after the car cools off.

 

[linksys42]

Liquid filled gauges will drop about 2 psi when the liquid get hot and pressure builds inside the gauge. Set it cold and leave it, it will go back up to 43.5 after the car cools off.

Really? I have never heard that before? Guess you learn something new every day. Would 4psi still be considered normal? Just out of curiosity what do you think might be screwing with my LTFT and STFT? They seem to be doing some strange things, with a load on the engine and cruising along my ltft go to +3 and my stft range from +3 to +9, but at idle they sit around -5 and free revving up to the rpm point where I am cruising at sits in the -5 area also? Thanks for all your help!